Conventionally, an exhaust purification apparatus is known in which a selective reducing type NOx catalyst (SCR catalyst) is disposed inside an exhaust pipe and NOx (nitrogen oxide) is reduced into nitrogen and water with ammonia as a reducing agent for decreasing the NOx in exhaust gas discharged from an internal combustion engine. For example, it is like the Patent Literature 1.
In an exhaust purification apparatus described in the Patent Literature 1, a urea solution is supplied from a urea solution injection nozzle arranged inside an exhaust pipe to exhaust gas, and ammonia is generated from the urea solution by heat of the exhaust gas so as to reduce NOx into nitrogen and water. However, there is a problem in that water of the urea solution remaining in a surface of the urea solution injection nozzle evaporates with the heat of the exhaust gas so that urea deposits and grows, thereby closing the exhaust pipe.
On the other hand, a two-fluid mixing type nozzle such as the urea solution injection nozzle is known in that pressurized air for atomizing medicinal liquid (coating liquid) is mixed with the coating liquid while being discharged to a tip of the nozzle so as to prevent the coating liquid from adhering to the tip of the nozzle and becoming a lump. For example, it is like the Patent Literature 2.
However, the nozzle described in the Patent Literature 2 prevents the coating liquid from adhering to the tip of the nozzle. In the case of injecting the urea solution upward like a urea solution injection nozzle in an exhaust purification apparatus for a ship, the urea solution adheres to the whole nozzle. Accordingly, when the art disclosed in the Patent Literature 1 is used, it is disadvantageous that deposition and growth of the urea cannot be prevented effectively.